[ben1040]

Anecdote is not the singular of data, but I have been able to send/receive long messages using Android and iPhone on AT&T.

Just yesterday I even noticed Android's core SMS app is even nice enough to tell you when the message is overflowing into a second SMS, so you know that you and the recipient will get billed for more than one SMS. Which brings me to another idea:

Perhaps the billing issue is more of a concern as well -- receiving concatenated messages certainly would cost more for (American) users not on unlimited SMS plans, and presumably would cost more for Twitter to send out through their gateway?